Airlines are more crowded than ever

The airlines' load factors -- a way to measure airlines' fullness -- were at record highs for the month of April: 81.6% system wide, 82.5% for domestic flights and 79.3% for international flights.

Over the past few years, U.S. airlines had cut capacity due to the sharp increase in fuel costs and then to match the lower demand during the recession. The DOT said the number of passengers has slowly increased during the first four moths of 2010 compared to the same period last year, but is still 9% lower than what it was for the same time period in 2008.

0:00/03:52Azul Airlines, the Brazilian JetBlue

Delta Air Lines (DAL, Fortune 500) carried more than passengers than any other U.S. airline in April while Southwest airlines carried the most domestic passengers and American Airlines (AMR, Fortune 500) carried the most international passengers, according the data in the release. 

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